Electron Heating Associated With Magnetic Reconnection in Foreshock Waves: Particle-In-Cell Simulation Analysis

Magnetic reconnection occurs in turbulent plasmas like shock transition regions, while its role in energy dissipation therein is not yet clear. We perform a 2D particle-in-cell simulation of foreshock waves and study electron heating associated with reconnection. The probability distribution of T-e exhibits a shift to higher values near reconnection X-lines compared to elsewhere. By examining the T-e evolution using the superposed epoch analysis, we find that T-e is higher in reconnection than in non-reconnecting current sheets, and T-e increases over the ion cyclotron time scale. The heating rate of T-e is 10%-40% m(i)V(A)(2), where V-A is the average ion Alfv & eacute;n speed in reconnection regions, which demonstrates the importance of reconnection in heating electrons. We further investigate the bulk electron energization mechanisms by decomposing j(e) E under guiding center approximations. Around the reconnection onset, E-|| dominates the total energization partly contributed by electron holes, and the perpendicular energization is dominated by the magnetization term associated with the gyro-motion in inhomogeneous fields. The Fermi mechanism contributes negative energization at early time mainly due to Hall effects, and later the outflow in the reconnection plane contributes more dominant positive values. After a couple of ion cyclotron periods from reconnection onset, the Fermi mechanism dominates the energization. A critical factor for initiating reconnection is to drive current sheets to the d(e)-scale thickness. The reconnection structures can be complicated due to flows originated from the ion-scale waves, and interactions between multiple reconnection sites. Visualizing such complicated features in simulations may assist future analysis of observation data.

Automated summary

We perform a simulation to study electron heating associated with magnetic reconnection in turbulent plasmas. The simulation shows that the electron temperature is higher near reconnection sites compared to other areas, and the heating rate of the electrons is influenced by the average ion Alfvén speed. We also investigate the mechanisms of electron energization and find that different mechanisms dominate at different stages of the reconnection process. The thickness of the current sheets plays a critical role in initiating reconnection.